title: Highly enantioselective synthesis of α,α-dialkylmalonates by phase-transfer catalytic desymmetrization.
abstract: A novel enantioselective synthetic method for the construction of a quaternary carbon center from malonates via phase-transfer catalytic (PTC) alkylation has been developed. The asymmetric α-alkylation of diphenylmethyl tert-butyl α-alkylmalonates with alkylating agents under phase-transfer catalysis conditions (aq 50% KOH, toluene, 0 °C) in the presence of (S,S)-3,4,5-trifluorophenyl-NAS bromide (8) as PTC catalyst afforded the corresponding α,α-dialkylmalonates in high chemical (up to 99%) and optical yields (up to 97% ee) which could be readily converted to versatile chiral intermediates. Notably, the direct double α-alkylations of diphenylmethyl tert-butyl malonate also provided the corresponding α,α-dialkylmalonates without loss of enantioselectivity. The synthetic potential of this method has been demonstrated by the preparation of α,α-dialkylamino acid and oxindole systems.
authors.affiliation: Research Institute of Pharmaceutical Sciences and College of Pharmacy, Seoul National University, Seoul 151-742, Korea.
authors.forename: Suckchang
authors.initials: S
authors.lastname: Hong
authors.forename: Jihye
authors.initials: J
authors.lastname: Lee
authors.forename: Minsik
authors.initials: M
authors.lastname: Kim
authors.forename: Yohan
authors.initials: Y
authors.lastname: Park
authors.forename: Cheonhyoung
authors.initials: C
authors.lastname: Park
authors.forename: Mi-hyun
authors.initials: MH
authors.lastname: Kim
authors.forename: Sang-sup
authors.initials: SS
authors.lastname: Jew
authors.forename: Hyeung-geun
authors.initials: HG
authors.lastname: Park
mesh_terms: D000478:Alkylation; D002384:Catalysis; D018360:Crystallography, X-Ray; D008314:Malonates / Q000138:chemical synthesis* / Q000737:chemistry; D008958:Models, Molecular; D015394:Molecular Structure; D044367:Phase Transition; D013237:Stereoisomerism
chemical_list: D008314:Malonates